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Ischaemic spinal cord lesion following percutaneous radiofrequency spinal rhizotomy
Pain, 45 (1991) 161-166 0 1991 Elsevier Science Publishers ADONIS 03043959910012OL
161 B.V. 0304-3959/91/$03.50
PAIN 01788
Clinical Note
Ischaemic spinal cord lesion following percutaneous radiofrequency spinal rhizotomy Henk M. Koning, Department
Hans G. Koster”
and Rob P.E. Niemeijer
of Anaesthesiology and a Department of Neurology, Medical Centre, Leeuwarden (The Netherlands)
(Received
26 October
1989, revision received
15 July 1990, accepted
15 November
1990)
Two patients are presented in whom percutaneous radiofrequency spinal rhizotomy was complicated suIuulary by contralateral paresis. Both patients were elderly and suffered from cardiac failure, chronic obstructive respiratory disease, and generalized vascular disease. Investigation of the paresis indicated a contralateral ischaemic cord lesion. It is suggested that local haemodynamic changes induced by heat-mediated rhizotomy may compromise oxygen delivery to the adjacent cord, especially in the presence of pre-existent cardiovascular disease. Key words: Complication,
Brown-Sequard
neural blockade; Percutaneous radiofrequency syndrome
Introduction
Techniques for interrupting spinal pain pathways are not free from risk even though meticulous attention to technique may reduce the complication rate considerably. Even those procedures which are advocated in elderly and infirm patients may present unexpected complications. Two patients with an ischaemic spinal cord lesion following percutaneous radiofrequency spinal rhizotomy are presented.
Case history 1 A 77-year-old woman had suffered for 2 years from post-herpetic neuralgia at Th4 on the left side. She also suffered from chronic obstructive lung disease, cardiac failure, angina pectoris and intermittent claudication. Her medication consisted of prednisone, sintromitis, furosemide, triamterene, nifedipine, isosorbidenitrate and ibuprofen. She had undergone various forms of pain treatment: medication (tryptizol and analgesics), physiotherapy, acupuncture, several epidural injections and transcutaneous electrical nerve stimulation. None
Correspondence to: H.M. Koning, M.D., Medical Centre Leeuwarden, Henri Dunantweg 2, 8934 AD Leeuwarden, The Netherlands.
spinal rhizotomy;
of these measures had helped, and she stated that she could no longer live with the pain. A left Th4 block was performed with 1 ml 0.5% bupivacaine. The pain was reduced to 30% for 4-6 h. She found the residual pain acceptable. It was decided to perform a percutaneous radiofrequency spinal rhizotomy at Th4. Under X-ray control, an SMK needle was placed in the left intervertebral foramen at Th4. Stimulation at 50 Hz and 1 V produced parestheses. Stimulation at 2 Hz produced no motoric contraction at 2 V. One millilitre of 2% xylocaine was injected through the needle. After 5 min, a lesion was made at 70 o C for 60 sec. The patient was transported to the recovery room where she stepped off the trolley into her bed. No motoric dysfunction was observed. Fifteen to 20 min after the procedure she felt a decrease in strength in her right leg. Ten minutes later she could not move her right leg at all. A neurologist was consulted. Paresis of the entire right leg was observed. Pain sensation was absent from Th6 downwards on the left side. Vibration sense was intact. An emergency CT scan was performed. A hyperdense spot was found in the spinal cord at level Th5 and 6 on the right anterior side. Nuclear magnetic resonance also demonstrated a lesion at Th5 and 6 (Fig. 1). Intravenous injection of gadolineum-DTPA pro-
162
duced no reaction, indicating an ischaemic lesion of the spinal cord. The complication was diagnosed as an incomplete Brown-Sequard syndrome. caused by a haemorrhagic infarction of the spinal cord. Some recovery was evident after 2 days. The paresis improved very slowly and after 2 months she could lift her leg. However, walking with support was achieved only with some difficulty. The original pain on the left side was diminished by 50%.
Case history 2
A 72-year-old woman had suffered for 7 months from post-herpetic neuralgia involving Th4 and 5 on the right side. She also had chronic obstructive lung disease, cardiac failure and hypertension. Her medication consisted of prednisone, salbutamol, theophylline, furosemide, triamterene, promethazine and ibuprofen. She had undergone various forms of pain treatment: medication (tryptizol and analgesics), physiotherapy, an epidural injection and transcutaneous electrical nerve stimulation. None of these measures provided adequate pain relief, and she stated that she could no longer live with the pain. A percutaneous radiofrequency spinal rhizotomy of Th4 and 5 was performed. Under X-ray control 2 SMK
Fig. 1. Nuclear
magnetic
resonance
study in patient
1, showing
an ischaemic
lesion at Th5 and 6 on the right side. A: sagittal;
B: transverse.
163
needles were placed in the right intervertebral foramen at Th4 and 5. Stimulation at 50 Hz produced parestheses at less than 1 V. Stimulation at 2 Hz produced no motoric contraction at 2 V. One millilitre of 2% xylocaine was injected through each needle. After 5 min a lesion was made at 70°C for 60 sec. The patient was transported to the recovery room where she stepped off the trolley into her bed. No motoric dysfunction was observed. Half an hour after the procedure she noticed she could not move her left leg. A neurologist was consulted. Paresis of the left leg was observed. Pain sensation was absent from Th6 downwards on the right side. Vibration sense was intact. An emergency CT scan was performed. No abnormalities were found. However, an emergency nuclear magnetic resonance scan revealed an ischaemic lesion at Th6 and 7 on the left anterior side (Fig. 2). An intravenous injection of gadolineum-DTPA produced no reaction. The complication was diagnosed as an incomplete Brown-Sequard syndrome, caused by an ischaemic lesion of the spinal cord. That same night she could move her left foot a little. The function of her left leg improved slowly. The original pain due to the post-herpetic neuralgia was diminished by 20%.
Fig. 2. Nuclear
magnetic
resonance
study in patient
2, showing
an ischaemic
lesion at Th6 and 7 on the left side. A: sagittal;
B: transverse.
164
Discussion
Percutan~us radiofr~uency spinal rhizotomy is considered to be an acceptable alternative in cases of chronic pain unresponsive to other conservative therapies. It has been reported that this procedure is helpful in patients suffering from post-herpetic neuralgia with prominent cutaneous hyperaesthesia [S]. The combined use of a fine thermocouple electrode, image intensifier, nerve stimulator, and radiofrequency lesion generator provides a relatively simple and safe procedure [5,9]. The technique has been particularly recommended for elderly or infirm patients [9]. The technique of percutaneous radiofrequency spinal rhizotomy involves the placement, under X-ray control, of a needle in the dorsal quadrant of the appropriate intervertebral foramen. The transverse projection confirms the posterior position within the foramen, and the anterior-posterior projection ensures that the needle tip does not advance further than a line connecting the facet joint spaces on the appropriate side. The stylet of the guide needle is replaced by a thermocouple electrode and electrical stimulation is used to verify that the root innervates the painful region. A tingling sensation in the appropriate dermatome at 50 Hz stimulation should be elicited by less than 1.0 V. Stimulation with 2 Hz is then performed and the voltage which gives motoric contraction must be more than twice the level of the sensory voltage. Local anaesthetic is injected and after S-10 min a lesion is made by a temperature of 70 o C maintained for 60 sec. Spinal thermocoagulation procedures are generally free from side effects, other than local contusion and oedema at the needle sites. However, 2 patients developed an incomplete Brown-Sequard syndrome on the opposite side. Initially, an accidental radiofrequency lesion in the spinal cord was considered. However, the procedure in both patients was carried out under X-ray control, and electrical stimulation gave sensations in the appropriate dermatome without motoric contraction, making a radiofrequency lesion in the spinal cord unlikely. The nuclear magnetic resonance study in both patients revealed an ischaemic lesion of the spinal cord on the opposite side, starting 1 thoracic segment below the level of the rhixotomy and involving 2 thoracic segments. The diagnosis of a radiofrequency lesion of the spinal cord was, therefore, rejected and a compromised vascular supply provoked by the p~cutan~us radiofrequency spinal rhizotomy was believed to be responsible for this complication. The spinal cord is supplied by spinal branches of the vertebral, deep cervical, intercostal and lumbar arteries; it can be divided into 3 areas, according to the blood supply (Fig. 3). The upper and lower areas are well perfused. However, the mid-thoracic area has poor circulation [4], the arteries being smaller and less numer-
Cervical
Upper thorac ic
Thoracolumbar
Fig. 3. The blood
supply of the spinat cord. The dotted critical zone of perfusion.
area is the
ous. The area of TM-8 is thus vulnerable for ischaemic lesions. Occasionally, a small artery is present at Th7, supplying the spinal cord. The spinal branches give rise to anterior and posterior radicular arteries which approach the spinal cord along the ventral and dorsal nerve roots (Fig. 4). The anterior radicular arteries are generally smaller. A small number (usually 4-9) are larger than the remainder and extend as far as the anterior median sulcus of the spinal cord, where they divide into ascending and descending branches. These branches anastomose with each other, and with the anterior spinal arteries above, to form a longitudinal vessel along the anterior median sulcus. From the anterior spinal artery the s&al arteries pass into the anterior median fissure. Here, each one passes either to the
165
right or left, to supply the anterior grey column, the base of the posterior grey column, including the dorsal nucleus, and the adjacent white matter. They are responsible for the supply of up to two-thirds of the cross-sectional area of the spinal cord [lo]. Ischaemic spinal cord lesions may be caused by haemodynamic dysfunction or by local changes in blood vessels [4]. The blood supply of the spinal cord depends on systemic haemodynamic factors. Impaired delivery of blood due to a diminished cardiac function and/or high venous pressure, as seen in car pulmonale, may therefore reduce the blood supply to the spinal cord. Ischaemic spinal cord lesions caused by haemodynamic dysfunction will occur particularly in the mid-thoracic region, because this area is poorly perfused and is often involved in generalized atherosclerosis [4]. Local changes in blood vessels supplying the spinal cord also lead to ischaemic lesions. The syndrome of the anterior spinal artery consists of paraparesis, dissociated sensibility, and occasionally stool and urine retention. Obstruction of a major radicular artery can cause an acute transverse myelopathy. The posterior spinal artery syndrome is rare, and produces interruption of proprioception. Interruption of a sulcal artery results in an ischaemic lesion of the medial and ventral part of the spinal cord. This lesion causes a homolateral motoric uniparesis, with absence of pain and touch sensation on the contralateral side. Vibration sense remains intact on both sides [6]. In both patients, percutaneous radiofrequency spinal rhizotomy provoked an ischaemic lesion of the spinal cord on the opposite side and 1 segment lower. Co-incidental local changes in the blood vessels supplying the spinal cord (e.g., vascular lesion, thrombosis, an atheromatous plaque or oedema) are feasible, but traumatic damage to the local vasculature is unlikely, as the lesion would then occur on the same side and at the same level. An area of the spinal cord on the opposite side was deprived of its blood supply. We postulate that the most likely explanation for this complication is a ‘steal’ effect of the local circulation, provoked by the percutaAnterior spinal artery
Fig. 4. A horizontal
PATIENT
1
2
RF- lesion III
lschaemic
lesion
Fig. 5. The localisation of the ischaemic lesion of the spinal cord, the site of the radiofrequency (RF) lesion and the blood supply of the spinal cord in both patients.
neous radiofrequency spinal rhizotomy. During the procedure, local heat at 70 o C was applied for 1 min to the foramen intervertebralis. One can assume that heat application will lead to local hyperaemia and vasodilatation. Normally, circulatory compensatory mechanisms would lead to an increase in the spinal cord blood supply. However, in patients whose blood supply to the spinal cord is already compromised, such as patients with diminished cardiac function and generalized atherosclerosis, the compensatory response may be absent, and blood will be diverted away from other areas of the spinal cord. Theoretically, the areas most likely to be involved are located on the opposite side, and distant from the origin of the arterial supply. This mechanism could account for the lesions observed in both patients (Fig. 5). The most likely site for this complication is the mid-thoracic area with its poor perfusion and its vulnerability to generalized atherosclerosis. Ischaemic spinal cord lesions following neural blocks have been described previously. Thrombosis of the posterior spinal artery has been reported to be a complication of intrathecal phenol injection [3]. Ischaemia of the anterior spinal artery has been reported following phenol injection intrathecally [S], in the stellate ganglion [7] and in the coeliac plexus [l]. A major radicular syndrome has also been reported following a coeliac blockade [2]. To our knowledge, percutaneous radiofrequency spinal rhizotomy has not previously been associated with ischaemic lesions of the spinal cord. Percutaneous radiofrequency spinal rhizotomy, especially in the thoracic area, may induce changes in the blood supply of the spinal cord which can lead to ischaemic lesions.
References
Posterior spinal
PATIENT
Right
Left
Right
Left
artery
view of the blood supply of the spinal cord.
1 Cherry, D.A. and Lamberty, J., Paraplegia following block, Anaesth. Intens. Care 12 (1984) 59-61.
coeliac plexus
7 GaliLia. E.J. and Lahiri, S.K., Paraplegia following coeliac plexus block with phenol, Br. J. Anaesth., 46 (1974) 539-540. 3 Hughes, J.T.. Thrombosis of the posterior spinal arteries: a complication of an intrathecal injection of phenol. Neurology. 20 ( 1970) 659-664. 4 Lazorthes, G.. La vascularisation de la moelle &pin&e. Rev. Neural.. 6 (1962) 535-5.57. 5 Pagura, J.R., Percutaneous radiofrequency spinal rhizotomy. Appl. Neurophysiol., 46 (1983) 13X-146. 6 Suchenwirth, R., Gibt es ein Syndrom der Arteria sulcocommis\uralis?, Nervenarzt, 44 (1973) 6044605.
7 Superville-Sovak, B.. Rasminsky, M. and Fmlayson. M.H.. C‘umplications of phenol neurolyais. Arch. Neural., 32 ( 1975) 226-22X. X Totokt. T.. Kate, T.. Nomoto. Y., Kurakazu. M. and Kanaseki. T.. Anterior spinal artery syndrome -- a complication of cervical intrathecal phenol injection. Pain. 6 (1979) 99-104. 9 Uematsu, S., Lldvarhelyi. G.B.. Benson. D.W. itnd Siebena, A.A.. Percutaneous radiofrequency rhizotomy. Surg. Neural.. 2 (1974) 319-325. l(J Warwick. R. and Williams. P.L., Gray‘s Anatomy. Longman. Edinburgh. 1973.
161 B.V. 0304-3959/91/$03.50
PAIN 01788
Clinical Note
Ischaemic spinal cord lesion following percutaneous radiofrequency spinal rhizotomy Henk M. Koning, Department
Hans G. Koster”
and Rob P.E. Niemeijer
of Anaesthesiology and a Department of Neurology, Medical Centre, Leeuwarden (The Netherlands)
(Received
26 October
1989, revision received
15 July 1990, accepted
15 November
1990)
Two patients are presented in whom percutaneous radiofrequency spinal rhizotomy was complicated suIuulary by contralateral paresis. Both patients were elderly and suffered from cardiac failure, chronic obstructive respiratory disease, and generalized vascular disease. Investigation of the paresis indicated a contralateral ischaemic cord lesion. It is suggested that local haemodynamic changes induced by heat-mediated rhizotomy may compromise oxygen delivery to the adjacent cord, especially in the presence of pre-existent cardiovascular disease. Key words: Complication,
Brown-Sequard
neural blockade; Percutaneous radiofrequency syndrome
Introduction
Techniques for interrupting spinal pain pathways are not free from risk even though meticulous attention to technique may reduce the complication rate considerably. Even those procedures which are advocated in elderly and infirm patients may present unexpected complications. Two patients with an ischaemic spinal cord lesion following percutaneous radiofrequency spinal rhizotomy are presented.
Case history 1 A 77-year-old woman had suffered for 2 years from post-herpetic neuralgia at Th4 on the left side. She also suffered from chronic obstructive lung disease, cardiac failure, angina pectoris and intermittent claudication. Her medication consisted of prednisone, sintromitis, furosemide, triamterene, nifedipine, isosorbidenitrate and ibuprofen. She had undergone various forms of pain treatment: medication (tryptizol and analgesics), physiotherapy, acupuncture, several epidural injections and transcutaneous electrical nerve stimulation. None
Correspondence to: H.M. Koning, M.D., Medical Centre Leeuwarden, Henri Dunantweg 2, 8934 AD Leeuwarden, The Netherlands.
spinal rhizotomy;
of these measures had helped, and she stated that she could no longer live with the pain. A left Th4 block was performed with 1 ml 0.5% bupivacaine. The pain was reduced to 30% for 4-6 h. She found the residual pain acceptable. It was decided to perform a percutaneous radiofrequency spinal rhizotomy at Th4. Under X-ray control, an SMK needle was placed in the left intervertebral foramen at Th4. Stimulation at 50 Hz and 1 V produced parestheses. Stimulation at 2 Hz produced no motoric contraction at 2 V. One millilitre of 2% xylocaine was injected through the needle. After 5 min, a lesion was made at 70 o C for 60 sec. The patient was transported to the recovery room where she stepped off the trolley into her bed. No motoric dysfunction was observed. Fifteen to 20 min after the procedure she felt a decrease in strength in her right leg. Ten minutes later she could not move her right leg at all. A neurologist was consulted. Paresis of the entire right leg was observed. Pain sensation was absent from Th6 downwards on the left side. Vibration sense was intact. An emergency CT scan was performed. A hyperdense spot was found in the spinal cord at level Th5 and 6 on the right anterior side. Nuclear magnetic resonance also demonstrated a lesion at Th5 and 6 (Fig. 1). Intravenous injection of gadolineum-DTPA pro-
162
duced no reaction, indicating an ischaemic lesion of the spinal cord. The complication was diagnosed as an incomplete Brown-Sequard syndrome. caused by a haemorrhagic infarction of the spinal cord. Some recovery was evident after 2 days. The paresis improved very slowly and after 2 months she could lift her leg. However, walking with support was achieved only with some difficulty. The original pain on the left side was diminished by 50%.
Case history 2
A 72-year-old woman had suffered for 7 months from post-herpetic neuralgia involving Th4 and 5 on the right side. She also had chronic obstructive lung disease, cardiac failure and hypertension. Her medication consisted of prednisone, salbutamol, theophylline, furosemide, triamterene, promethazine and ibuprofen. She had undergone various forms of pain treatment: medication (tryptizol and analgesics), physiotherapy, an epidural injection and transcutaneous electrical nerve stimulation. None of these measures provided adequate pain relief, and she stated that she could no longer live with the pain. A percutaneous radiofrequency spinal rhizotomy of Th4 and 5 was performed. Under X-ray control 2 SMK
Fig. 1. Nuclear
magnetic
resonance
study in patient
1, showing
an ischaemic
lesion at Th5 and 6 on the right side. A: sagittal;
B: transverse.
163
needles were placed in the right intervertebral foramen at Th4 and 5. Stimulation at 50 Hz produced parestheses at less than 1 V. Stimulation at 2 Hz produced no motoric contraction at 2 V. One millilitre of 2% xylocaine was injected through each needle. After 5 min a lesion was made at 70°C for 60 sec. The patient was transported to the recovery room where she stepped off the trolley into her bed. No motoric dysfunction was observed. Half an hour after the procedure she noticed she could not move her left leg. A neurologist was consulted. Paresis of the left leg was observed. Pain sensation was absent from Th6 downwards on the right side. Vibration sense was intact. An emergency CT scan was performed. No abnormalities were found. However, an emergency nuclear magnetic resonance scan revealed an ischaemic lesion at Th6 and 7 on the left anterior side (Fig. 2). An intravenous injection of gadolineum-DTPA produced no reaction. The complication was diagnosed as an incomplete Brown-Sequard syndrome, caused by an ischaemic lesion of the spinal cord. That same night she could move her left foot a little. The function of her left leg improved slowly. The original pain due to the post-herpetic neuralgia was diminished by 20%.
Fig. 2. Nuclear
magnetic
resonance
study in patient
2, showing
an ischaemic
lesion at Th6 and 7 on the left side. A: sagittal;
B: transverse.
164
Discussion
Percutan~us radiofr~uency spinal rhizotomy is considered to be an acceptable alternative in cases of chronic pain unresponsive to other conservative therapies. It has been reported that this procedure is helpful in patients suffering from post-herpetic neuralgia with prominent cutaneous hyperaesthesia [S]. The combined use of a fine thermocouple electrode, image intensifier, nerve stimulator, and radiofrequency lesion generator provides a relatively simple and safe procedure [5,9]. The technique has been particularly recommended for elderly or infirm patients [9]. The technique of percutaneous radiofrequency spinal rhizotomy involves the placement, under X-ray control, of a needle in the dorsal quadrant of the appropriate intervertebral foramen. The transverse projection confirms the posterior position within the foramen, and the anterior-posterior projection ensures that the needle tip does not advance further than a line connecting the facet joint spaces on the appropriate side. The stylet of the guide needle is replaced by a thermocouple electrode and electrical stimulation is used to verify that the root innervates the painful region. A tingling sensation in the appropriate dermatome at 50 Hz stimulation should be elicited by less than 1.0 V. Stimulation with 2 Hz is then performed and the voltage which gives motoric contraction must be more than twice the level of the sensory voltage. Local anaesthetic is injected and after S-10 min a lesion is made by a temperature of 70 o C maintained for 60 sec. Spinal thermocoagulation procedures are generally free from side effects, other than local contusion and oedema at the needle sites. However, 2 patients developed an incomplete Brown-Sequard syndrome on the opposite side. Initially, an accidental radiofrequency lesion in the spinal cord was considered. However, the procedure in both patients was carried out under X-ray control, and electrical stimulation gave sensations in the appropriate dermatome without motoric contraction, making a radiofrequency lesion in the spinal cord unlikely. The nuclear magnetic resonance study in both patients revealed an ischaemic lesion of the spinal cord on the opposite side, starting 1 thoracic segment below the level of the rhixotomy and involving 2 thoracic segments. The diagnosis of a radiofrequency lesion of the spinal cord was, therefore, rejected and a compromised vascular supply provoked by the p~cutan~us radiofrequency spinal rhizotomy was believed to be responsible for this complication. The spinal cord is supplied by spinal branches of the vertebral, deep cervical, intercostal and lumbar arteries; it can be divided into 3 areas, according to the blood supply (Fig. 3). The upper and lower areas are well perfused. However, the mid-thoracic area has poor circulation [4], the arteries being smaller and less numer-
Cervical
Upper thorac ic
Thoracolumbar
Fig. 3. The blood
supply of the spinat cord. The dotted critical zone of perfusion.
area is the
ous. The area of TM-8 is thus vulnerable for ischaemic lesions. Occasionally, a small artery is present at Th7, supplying the spinal cord. The spinal branches give rise to anterior and posterior radicular arteries which approach the spinal cord along the ventral and dorsal nerve roots (Fig. 4). The anterior radicular arteries are generally smaller. A small number (usually 4-9) are larger than the remainder and extend as far as the anterior median sulcus of the spinal cord, where they divide into ascending and descending branches. These branches anastomose with each other, and with the anterior spinal arteries above, to form a longitudinal vessel along the anterior median sulcus. From the anterior spinal artery the s&al arteries pass into the anterior median fissure. Here, each one passes either to the
165
right or left, to supply the anterior grey column, the base of the posterior grey column, including the dorsal nucleus, and the adjacent white matter. They are responsible for the supply of up to two-thirds of the cross-sectional area of the spinal cord [lo]. Ischaemic spinal cord lesions may be caused by haemodynamic dysfunction or by local changes in blood vessels [4]. The blood supply of the spinal cord depends on systemic haemodynamic factors. Impaired delivery of blood due to a diminished cardiac function and/or high venous pressure, as seen in car pulmonale, may therefore reduce the blood supply to the spinal cord. Ischaemic spinal cord lesions caused by haemodynamic dysfunction will occur particularly in the mid-thoracic region, because this area is poorly perfused and is often involved in generalized atherosclerosis [4]. Local changes in blood vessels supplying the spinal cord also lead to ischaemic lesions. The syndrome of the anterior spinal artery consists of paraparesis, dissociated sensibility, and occasionally stool and urine retention. Obstruction of a major radicular artery can cause an acute transverse myelopathy. The posterior spinal artery syndrome is rare, and produces interruption of proprioception. Interruption of a sulcal artery results in an ischaemic lesion of the medial and ventral part of the spinal cord. This lesion causes a homolateral motoric uniparesis, with absence of pain and touch sensation on the contralateral side. Vibration sense remains intact on both sides [6]. In both patients, percutaneous radiofrequency spinal rhizotomy provoked an ischaemic lesion of the spinal cord on the opposite side and 1 segment lower. Co-incidental local changes in the blood vessels supplying the spinal cord (e.g., vascular lesion, thrombosis, an atheromatous plaque or oedema) are feasible, but traumatic damage to the local vasculature is unlikely, as the lesion would then occur on the same side and at the same level. An area of the spinal cord on the opposite side was deprived of its blood supply. We postulate that the most likely explanation for this complication is a ‘steal’ effect of the local circulation, provoked by the percutaAnterior spinal artery
Fig. 4. A horizontal
PATIENT
1
2
RF- lesion III
lschaemic
lesion
Fig. 5. The localisation of the ischaemic lesion of the spinal cord, the site of the radiofrequency (RF) lesion and the blood supply of the spinal cord in both patients.
neous radiofrequency spinal rhizotomy. During the procedure, local heat at 70 o C was applied for 1 min to the foramen intervertebralis. One can assume that heat application will lead to local hyperaemia and vasodilatation. Normally, circulatory compensatory mechanisms would lead to an increase in the spinal cord blood supply. However, in patients whose blood supply to the spinal cord is already compromised, such as patients with diminished cardiac function and generalized atherosclerosis, the compensatory response may be absent, and blood will be diverted away from other areas of the spinal cord. Theoretically, the areas most likely to be involved are located on the opposite side, and distant from the origin of the arterial supply. This mechanism could account for the lesions observed in both patients (Fig. 5). The most likely site for this complication is the mid-thoracic area with its poor perfusion and its vulnerability to generalized atherosclerosis. Ischaemic spinal cord lesions following neural blocks have been described previously. Thrombosis of the posterior spinal artery has been reported to be a complication of intrathecal phenol injection [3]. Ischaemia of the anterior spinal artery has been reported following phenol injection intrathecally [S], in the stellate ganglion [7] and in the coeliac plexus [l]. A major radicular syndrome has also been reported following a coeliac blockade [2]. To our knowledge, percutaneous radiofrequency spinal rhizotomy has not previously been associated with ischaemic lesions of the spinal cord. Percutaneous radiofrequency spinal rhizotomy, especially in the thoracic area, may induce changes in the blood supply of the spinal cord which can lead to ischaemic lesions.
References
Posterior spinal
PATIENT
Right
Left
Right
Left
artery
view of the blood supply of the spinal cord.
1 Cherry, D.A. and Lamberty, J., Paraplegia following block, Anaesth. Intens. Care 12 (1984) 59-61.
coeliac plexus
7 GaliLia. E.J. and Lahiri, S.K., Paraplegia following coeliac plexus block with phenol, Br. J. Anaesth., 46 (1974) 539-540. 3 Hughes, J.T.. Thrombosis of the posterior spinal arteries: a complication of an intrathecal injection of phenol. Neurology. 20 ( 1970) 659-664. 4 Lazorthes, G.. La vascularisation de la moelle &pin&e. Rev. Neural.. 6 (1962) 535-5.57. 5 Pagura, J.R., Percutaneous radiofrequency spinal rhizotomy. Appl. Neurophysiol., 46 (1983) 13X-146. 6 Suchenwirth, R., Gibt es ein Syndrom der Arteria sulcocommis\uralis?, Nervenarzt, 44 (1973) 6044605.
7 Superville-Sovak, B.. Rasminsky, M. and Fmlayson. M.H.. C‘umplications of phenol neurolyais. Arch. Neural., 32 ( 1975) 226-22X. X Totokt. T.. Kate, T.. Nomoto. Y., Kurakazu. M. and Kanaseki. T.. Anterior spinal artery syndrome -- a complication of cervical intrathecal phenol injection. Pain. 6 (1979) 99-104. 9 Uematsu, S., Lldvarhelyi. G.B.. Benson. D.W. itnd Siebena, A.A.. Percutaneous radiofrequency rhizotomy. Surg. Neural.. 2 (1974) 319-325. l(J Warwick. R. and Williams. P.L., Gray‘s Anatomy. Longman. Edinburgh. 1973.